Does Your Roof Need a Good Scrubbing?

By John Voket


I have tackled a lot of household chores in these columns, but we've never addressed the issue of roof cleaning. Although a quick search of roof cleaning companies brings up thousands across every region of the U.S., offering a variety of services from chemical applications to pressure washing, which one gets the job done best?

One company out of Portland, OR ( reports that many homeowners are surprised to discover that once-clean asphalt shingles are slowly being covered with a form of roof mold or mildew that appears as a light discoloration and spreads down the roof toward the gutters. Black roof stains are caused by a form of algae that has been around for years, typically found in the woods on the north side of trees or on exposed rocks.

Today this black algae is termed a roof shingle algae because of the annoying discoloration that appears on this roofing material. The roof algae actually feed on crushed limestone that is present in shingles from most asphalt roof manufacturers.

The algae are spread by wind and animals from roof to roof and are almost impossible to prevent.

The report states that high pressure jet washing or scraping of roofs is not recommended by professionals as both methods remove granules from the protective coating. Each time these aggressive cleaning methods are used, tiles are made more porous.

When granules have been removed, the roof stays damp, encouraging fungal growth to return. In addition, spores are not killed by these methods, meaning in a short time the problem will be worse than before.

The purpose of the clean-up process is to eliminate mold and fungal growth and to remove contaminated materials. Simply killing the mold with a chemical is not enough. The mold must be removed since the chemicals and proteins, which cause a reaction in humans, are still present, even in dead mold, according to the report.

Removing mold from the roof of a house is not only important in the prevention of a number of serious health conditions, but also gives an overall better look to the house.


Reprinted with permission from RISMedia. ©2013. All rights reserved.